Bioresorbable Scaffolds Based on Fibroin for Bone Tissue Regeneration

Using the tissue-engineered constructs based on scaffolds that imitate the extracellular matrix of living tissues unveils new opportunities in the treatment of various pathologies and injuries associated with tissue and organ damage. Silk fibroin of silkworm Bombyx mori is a biocompatible and bioresorbable polymer with high mechanical strength and elasticity that allows creating scaffolds on its basis for regeneration of various tissues, including bone. In the present work, fibroin scaffolds were obtained. They were designed in the form of porous sponges, films, and hybrid scaffolds of a bilayer structure in which the porous sponge threedimensional structure is limited on one side by a film. The structure of the scaffolds and their biocompatibility were studied: immortalized and primary fibroblasts, as well as the osteoblast-like cells, have been shown to successfully adhere and proliferate on the surface of the studied scaffolds. Numerous osteogenesis foci have been observed in the implant region 4 weeks after the fibroin porous scaffold implantation in the in vivo experiments in a rat femoral bone defect model indicating the osteoconduction of the scaffolds.     

Evaluating the biodegradability of Gelatin/Siloxane/Hydroxyapatite (GS-Hyd) complex in vivo and its ability for adhesion and proliferation of rat bone marrow mesenchymal stem cells

Recent studies have shown that the use of biomaterials and new biodegradable scaffolds for repair or regeneration of damaged tissues is of vital importance. Scaffolds used in tissue engineering should be biodegradable materials with three-dimensional structures which guide the growth and differentiation of the cells. They also tune physical, chemical and biological properties for efficient supplying of the cells to the selected tissues and have proper porosity along with minimal toxic effects. In this manner, the study of these characteristics is a giant stride towards scaffold design. In this study, Gelatin/Siloxane/Hydroxyapatite (GS-Hyd) scaffold was synthesized and its morphology, in vivo biodegradability, cytotoxic effects and ability for cell adhesion were investigated using mesenchymal stem cells (MSCs). The cells were treated with different volumes of the scaffold suspension for evaluation of its cytotoxic effects. The MSCs were also seeded on scaffolds and cultured for 2 weeks to evaluate the ability of the scaffold in promoting of cell adhesion and growth. To check the biodegradability of the scaffold in vivo, scaffolds were placed in the rat body for 21 days in three different positions of thigh muscle, testicle, and liver and they were analyzed by scanning electron microscopy (SEM) and weight changes. According to the results of the viability of this study, no cytotoxic effects of GS-Hyd scaffold was found on the cells and MSCs could adhere on the scaffold with expanding their elongations and forming colonies. The rate of degradation as assessed by weight loss was significant within each group along with significant differences between different tissues at the same time point. SEM micrographs also indicated the obvious morphological changes on the surface of the particles and diameter of the pores through different stages of implantation. The greatest amount of degradation happened to the scaffold particles implanted into the muscle, followed by testicle and liver, respectively.     

Osteostimulation scaffolds of stem cells: BMP‐7‐derived peptide‐decorated alginate porous scaffolds promote the aggregation and osteo‐differentiation of human mesenchymal stem cells

The scaffolds for stem cell‐based bone tissue engineering should hold the ability to guide stem cells osteo‐differentiating. Otherwise, stem cells will differentiate into unwanted cell types or will form tumors in vivo. Alginate, a natural polysaccharide with great biocompatibility, was widely used in biomedical applications. However, the limited bioactivity and poor osteogenesis capability of pristine alginate hampered its further application in tissue engineering. In this work, a bone forming peptide‐1 (BFP‐1), derived from bone morphogenetic protein‐7, was grafted to alginate polymer chains to prepare peptide‐decorated alginate porous scaffolds (pep‐APS) for promoting osteo‐differentiation of human mesenchymal stem cells (hMSCs). SEM images of pep‐APS exhibited porous structure with about 90% porosity (pore size 100–300 μm), which was appropriate for hMSCs ingrowth. The adhesion, proliferation and aggregation of hMSCs grown on pep‐APS were enhanced in vitro. Moreover, pep‐APS promoted the alkaline phosphatase (ALP) activity of hMSCs, and the osteo‐related genes expression was obviously up‐regulated. The immunochemical staining and western blot analysis results showed high expression level of OCN and Col1a1 in the hMSCs grown on pep‐APS. This work provided a facile and valid strategy to endow the alginate polymers themselves with specific bioactivity and prepare osteopromoting scaffold with enhanced osteogenesis ability, possessing potential applications in stem cell therapy and regenerative medicine.     

The restoration of full-thickness cartilage defects with mesenchymal stem cells (MSCs) loaded and cross-linked bilayer collagen scaffolds on rabbit model

Cartilage has a limited self-repair capability and the repair of large cartilage defects remains a challenge in clinic. This study aimed to investigate the effect of mesenchymal stem cells (MSCs) loaded three-dimensional bilayer collagen scaffold for cartilage repair. Cross-linked three-dimensional bilayer collagen scaffolds seeded with or without MSCs were implanted into large cartilage defects (4 mm in diameter; 3 mm in depth) in rabbit knees. The untreated cartilage defects served as control. The tissue response was evaluated at 6 and 12 weeks after implantation by general histology and semi-quantitative histological grading systems. In addition, the repaired tissues were evaluated by mechanical test at 12 weeks after implantation. The MSCs-loaded collagen scaffold group showed the most hyaline cartilage, highest histological scores and compressive modulus. Moreover, it showed a good integration with the subchondral bone and adjacent cartilage. The structure of the novel bilayer collagen scaffolds provided architectural support for the differentiation of MSCs and demonstrated successful induction of in vivo chondrogenesis. These findings suggested that MSCs-loaded bilayer collagen scaffold could be an appealing candidate to be used for cartilage regeneration.     

Comparative evaluation of in vivo osteogenic differentiation of fetal and adult mesenchymal stem cell in rat critical-sized femoral defect model

Mesenchymal stem cells (MSCs) can be obtained from various sources. MSCs from different origins appear to have different preferences for differentiation. In this study, we have compared the in vivo osteogenic potential of adult MSCs from adipose tissue (AT) and bone marrow (BM) with fetal MSCs from umbilical cord (UC) and umbilical cord blood (UCB) by using a rat critical-sized femoral defect model. We have also sought to determine whether pretreatment with an osteogenic medium promotes osteogenesis in MSCs. Study groups were divided as follows: (1) defect only, (2) scaffold only, (3) AT MSCs in scaffolds, (4) BM MSCs in scaffolds, (5) UC MSCs in scaffolds and (6) UCB MSCs in scaffolds. Groups with MSCs were further divided with respect to their pretreatment. At 12 weeks after surgery, in vivo osteogenesis was measured radiographically and by micro-computed tomography (CT). Based on quantitative assessment by micro-CT, no significant difference of the mean bone volume fraction value (BV/TV) was seen between adult MSCs (AT and BM MSCs) and fetal MSCs (UC and UCB MSCs). The mean BV/TVs were significantly higher in non-pretreated BM MSC (14.2±1.4%) and UCB MSC (14.0±1.2%) and pretreated UC MSC (14.8±2.0%) than in those with the scaffold only (11.3±1.3%; P<0.05). In addition, AT (from 10.4±1.2% to 13.1±2.2%) and UC (from 10.3±0.7% to 14.8±2.0%) MSCs from solid tissues showed a significant increase in the mean BV/TV with pretreatment (P<0.05). In contrast, BM MSC (from 14.2±1.4% to 10.9±1.2%) and UCB MSC (from 14.0±1.2% to 11.6±1.0%) from non-solid tissues showed a significant decrease with pretreatment (P<0.05).     

Enhanced Healing of Rat Calvarial Defects with MSCs Loaded on BMP-2 Releasing Chitosan/Alginate/Hydroxyapatite Scaffolds

In this study, we designed a chitosan/alginate/hydroxyapatite scaffold as a carrier for recombinant BMP-2 (CAH/B2), and evaluated the release kinetics of BMP-2. We evaluated the effect of the CAH/B2 scaffold on the viability and differentiation of bone marrow mesenchymal stem cells (MSCs) by scanning electron microscopy, MTS, ALP assay, alizarin-red staining and qRT-PCR. Moreover, MSCs were seeded on scaffolds and used in a 8 mm rat calvarial defect model. New bone formation was assessed by radiology, hematoxylin and eosin staining 12 weeks postoperatively. We found the release kinetics of BMP-2 from the CAH/B2 scaffold were delayed compared with those from collagen gel, which is widely used for BMP-2 delivery. The BMP-2 released from the scaffold increased MSC differentiation and did not show any cytotoxicity. MSCs exhibited greater ALP activity as well as stronger calcium mineral deposition, and the bone-related markers Col1α, osteopontin, and osteocalcin were upregulated. Analysis of in vivo bone formation showed that the CAH/B2 scaffold induced more bone formation than other groups. This study demonstrates that CAH/B2 scaffolds might be useful for delivering osteogenic BMP-2 protein and present a promising bone regeneration strategy.     

A cell leakproof PLGA‐collagen hybrid scaffold for cartilage tissue engineering

A cell leakproof porous poly(DL ‐lactic‐co‐glycolic acid) (PLGA)‐collagen hybrid scaffold was prepared by wrapping the surfaces of a collagen sponge except the top surface for cell seeding with a bi‐layered PLGA mesh. The PLGA‐collagen hybrid scaffold had a structure consisting of a central collagen sponge formed inside a bi‐layered PLGA mesh cup. The hybrid scaffold showed high mechanical strength. The cell seeding efficiency was 90.0% when human mesenchymal stem cells (MSCs) were seeded in the hybrid scaffold. The central collagen sponge provided enough space for cell loading and supported cell adhesion, while the bi‐layered PLGA mesh cup protected against cell leakage and provided high mechanical strength for the collagen sponge to maintain its shape during cell culture. The MSCs in the hybrid scaffolds showed round cell morphology after 4 weeks culture in chondrogenic induction medium. Immunostaining demonstrated that type II collagen and cartilaginous proteoglycan were detected in the extracellular matrices. Gene expression analyses by real‐time PCR showed that the genes encoding type II collagen, aggrecan, and SOX9 were upregulated. These results indicated that the MSCs differentiated and formed cartilage‐like tissue when being cultured in the cell leakproof PLGA‐collagen hybrid scaffold. The cell leakproof PLGA‐collagen hybrid scaffolds should be useful for applications in cartilage tissue engineering. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Porous Tantalum Coatings Prepared by Vacuum Plasma Spraying Enhance BMSCs Osteogenic Differentiation and Bone Regeneration In Vitro and In Vivo

Tantalum, as a potential metallic implant biomaterial, is attracting more and more attention because of its excellent anticorrosion and biocompatibility. However, its significantly high elastic modulus and large mechanical incompatibility with bone tissue make it unsuitable for load-bearing implants. In this study, porous tantalum coatings were first successfully fabricated on titanium substrates by vacuum plasma spraying (VPS), which would exert the excellent biocompatibility of tantalum and alleviate the elastic modulus of tantalum for bone tissue. We evaluated cytocompatibility and osteogenesis activity of the porous tantalum coatings using human bone marrow stromal cells (hBMSCs) and its ability to repair rabbit femur bone defects. The morphology and actin cytoskeletons of hBMSCs were observed via electron microscopy and confocal, and the cell viability, proliferation and osteogenic differentiation potential of hBMSCs were examined quantitatively by PrestoBlue assay, Ki67 immunofluorescence assay, real-time PCR technology and ALP staining. For in vivo detection, the repaired femur were evaluated by histomorphology and double fluorescence labeling 3 months postoperation. Porous tantalum coating surfaces promoted hBMSCs adhesion, proliferation, osteogenesis activity and had better osseointegration and faster new bone formation rate than titanium coating control. Our observation suggested that the porous tantalum coatings had good biocompatibility and could enhance osseoinductivity in vitro and promote new bone formation in vivo. The porous tantalum coatings prepared by VPS is a promising strategy for bone regeneration.     

Isolation of Human Mesenchymal Stem Cells and their Cultivation on the Porous Bone Matrix

Mesenchymal stem cells (MSCs) have a differentiation potential towards osteoblastic lineage when they are stimulated with soluble factors or specific biomaterials. This work presents a novel option for the delivery of MSCs from human amniotic membrane (AM-hMSCs) that employs bovine bone matrix Nukbone (NKB) as a scaffold. Thus, the application of MSCs in repair and tissue regeneration processes depends principally on the efficient implementation of the techniques for placing these cells in a host tissue. For this reason, the design of biomaterials and cellular scaffolds has gained importance in recent years because the topographical characteristics of the selected scaffold must ensure adhesion, proliferation and differentiation into the desired cell lineage in the microenvironment of the injured tissue. This option for the delivery of MSCs from human amniotic membrane (AM-hMSCs) employs bovine bone matrix as a cellular scaffold and is an efficient culture technique because the cells respond to the topographic characteristics of the bovine bone matrix Nukbone (NKB), i.e., spreading on the surface, macroporous covering and colonizing the depth of the biomaterial, after the cell isolation process. We present the procedure for isolating and culturing MSCs on a bovine matrix.     

The biocompatibility of calcium phosphate cements containing alendronate-loaded PLGA microparticles in?vitro

The composite of poly-lactic-co-glycolic acid (PLGA) and calcium phosphate cements (CPC) are currently widely used in bone tissue engineering. However, the properties and biocompatibility of the alendronate-loaded PLGA/CPC (APC) porous scaffolds have not been characterized. APC scaffolds were prepared by a solid/oil/water emulsion solvent evaporation method. The morphology, porosity, and mechanical strength of the scaffolds were characterized. Bone marrow mesenchymal stem cells (BMSCs) from rabbit were cultured, expanded and seeded on the scaffolds, and the cell morphology, adhesion, proliferation, cell cycle and osteogenic differentiation of BMSCs were determined. The results showed that the APC scaffolds had a porosity of 67.43 ± 4.2% and pore size of 213 ± 95 µm. The compressive strength for APC was 5.79 ± 1.21 MPa, which was close to human cancellous bone. The scanning electron microscopy, cell counting kit-8 assay, flow cytometry and ALP activity revealed that the APC scaffolds had osteogenic potential on the BMSCs in vitro and exhibited excellent biocompatibility with engineered bone tissue. APC scaffolds exhibited excellent biocompatibility and osteogenesis potential and can potentially be used for bone tissue engineering.     

Use of platelet lysate for bone regeneration - are we ready for clinical translation?

Current techniques to improve bone regeneration following trauma or tumour resection involve the use of autograft bone or its substitutes supplemented with osteoinductive growth factors and/or osteogenic cells such as mesenchymal stem cells(MSCs).Although MSCs are most commonly grown in media containing fetal calf serum,human platelet lysate(PL) offers an effective alternative.Bone marrow- derived MSCs grown in PLcontaining media display faster proliferation whilst maintaining good osteogenic differentiation capacity.Limited pre-clinical investigations using PL-expanded MSCs seeded onto osteoconductive scaffolds indicate good potential of such constructs to repair bone in vivo.In an alternative approach,nude PL-coated scaffolds without seeded MSCs have been proposed as novel regenerative medicine devices.Even though methods to coat scaffolds with PL vary,in vitro studies suggest that PL allows for MSC adhesion,migration and differentiation inside these scaffolds.Increased new bone formation and vascularisation in comparison to uncoated scaffolds have also been observed in vivo.This review outlines the state-of-the-art research in the field of PL for ex vivo MSC expansion and in vivo bone regeneration.To minimise inconsistency between the studies,further work is required towards standardisation of PL preparation in terms of the starting material,platelet concentration,leukocyte depletion,and the method of platelet lysis.PL quality control procedures and its "potency" assessment are urgently needed,which could include measurements of key growth and attachment factors important for MSC maintenance and differentiation.Furthermore,different PL formulations could be tailor-made for specific bone repair indications.Such measures would undoubtedly speed up clinical translation of PL-based treatments for bone regeneration.     

Collagen-Hydroxyapatite Scaffolds Induce Human Adipose Derived Stem Cells Osteogenic Differentiation In Vitro

Mesenchymal stem cells (MSCs) play a crucial role in regulating normal skeletal homeostasis and, in case of injury, in bone healing and reestablishment of skeletal integrity. Recent scientific literature is focused on the development of bone regeneration models where MSCs are combined with biomimetic three-dimensional scaffolds able to direct MSC osteogenesis. In this work the osteogenic potential of human MSCs isolated from adipose tissue (hADSCs) has been evaluated in vitro in combination with collagen/Mg doped hydroxyapatite scaffolds. Results demonstrate the high osteogenic potential of hADSCs when cultured in specific differentiation induction medium, as revealed by the Alizarin Red S staining and gene expression profile analysis. In combination with collagen/hydroxyapatite scaffold, hADSCs differentiate into mature osteoblasts even in the absence of specific inducing factors; nevertheless, the supplement of the factors markedly accelerates the osteogenic process, as confirmed by the expression of specific markers of pre-osteoblast and mature osteoblast stages, such as osterix, osteopontin (also known as bone sialoprotein I), osteocalcin and specific markers of extracellular matrix maturation and mineralization stages, such as ALPL and osteonectin. Hence, the present work demonstrates that the scaffold per se is able to induce hADSCs differentiation, while the addition of osteo-inductive factors produces a significant acceleration of the osteogenic process. This observation makes the use of our model potentially interesting in the field of regenerative medicine for the treatment of bone defects.     

The effect of autologous bone marrow stromal cells differentiated on scaffolds for canine tibial bone reconstruction

Bone marrow contains mesenchymal stem cells that form many tissues. Various scaffolds are available for bone reconstruction by tissue engineering. Osteoblastic differentiated bone marrow stromal cells (BMSC) promote osteogenesis on scaffolds and stimulate bone regeneration. We investigated the use of cultured autologous BMSC on different scaffolds for healing defects in tibias of adult male canines. BMSC were isolated from canine humerus bone marrow, differentiated into osteoblasts in culture and loaded onto porous ceramic scaffolds including hydroxyapatite 1, hydroxyapatite gel and calcium phosphate. Osteoblast differentiation was verified by osteonectine and osteocalcine immunocytochemistry. The scaffolds with stromal cells were implanted in the tibial defect. Scaffolds without stromal cells were used as controls. Sections from the defects were processed for histological, ultrastructural, immunohistochemical and histomorphometric analyses to analyze the healing of the defects. BMSC were spread, allowed to proliferate and differentiate to osteoblasts as shown by alizarin red histochemistry, and osteocalcine and osteonectine immunostaining. Scanning electron microscopy showed that BMSC on the scaffolds were more active and adhesive to the calcium phosphate scaffold compared to the others. Macroscopic bone formation was observed in all groups, but scaffolds with stromal cells produced significantly better results. Bone healing occurred earlier and faster with stromal cells on the calcium phosphate scaffold and produced more callus compared to other scaffolds. Tissue healing and osteoblastic marker expression also were better with stromal cells on the scaffolds. Increased trabecula formation, cell density and decreased fibrosis were observed in the calcium phosphate scaffold with stromal cells. Autologous cultured stromal cells on the scaffolds were useful for healing of canine tibial bone defects. The calcium phosphate scaffold was the best for both cell differentiation in vitro and bone regeneration in vivo. It may be possible to improve healing of bone defects in humans using stem cells from bone marrow.     

IGFBP3 deposited in the human umbilical cord mesenchymal stem cell‐secreted extracellular matrix promotes bone formation

The extracellular matrix (ECM) contains rich biological cues for cell recruitment, proliferationm, and even differentiation. The osteoinductive potential of scaffolds could be enhanced through human bone marrow mesenchymal stem cell (hBMSC) directly depositing ECM on surface of scaffolds. However, the role and mechanism of human umbilical cord mesenchymal stem cells (hUCMSC)‐secreted ECM in bone formation remain unknown. We tested the osteoinductive properties of a hUCMSC‐secreted ECM construct (hUCMSC‐ECM) in a large femur defect of a severe combined immunodeficiency (SCID) mouse model. The hUCMSC‐ECM improved the colonization of endogenous MSCs and bone regeneration, similar to the hUCMSC‐seeded scaffold and superior to the scaffold substrate. Besides, the hUCMSC‐ECM enhanced the promigratory molecular expressions of the homing cells, including CCR2 and TβRI. Furthermore, the hUCMSC‐ECM increased the number of migrated MSCs by nearly 3.3 ± 0.1‐fold, relative to the scaffold substrate. As the most abundant cytokine deposited in the hUCMSC‐ECM, insulin‐like growth factor binding protein 3 (IGFBP3) promoted hBMSC migration in the TβRI/II‐ and CCR2‐dependent mechanisms. The hUCMSC‐ECM integrating shRNA‐mediated silencing of Igfbp3 that down‐regulated IGFBP3 expression by approximately 60%, reduced the number of migrated hBMSCs by 47%. In vivo, the hUCMSC‐ECM recruited 10‐fold more endogenous MSCs to initiate bone formation compared to the scaffold substrate. The knock‐down of Igfbp3 in the hUCMSC‐ECM inhibited nearly 60% of MSC homing and bone regeneration capacity. This research demonstrates that IGFBP3 is an important MSC homing molecule and the therapeutic potential of hUCMSC‐ECM in bone regeneration is enhanced by improving MSC homing in an IGFBP3‐dependent mechanism.     

A new method of fabricating robust freeform 3D ceramic scaffolds for bone tissue regeneration

Fabrication of three‐dimensional (3D) scaffolds with appropriate mechanical properties and desired architecture for promoting cell growth and new tissue formation is one of the most important efforts in tissue engineering field. Scaffolds fabricated from bioactive ceramic materials such as hydroxyapatite and tricalcium phosphate show promise because of their biological ability to support bone tissue regeneration. However, the use of ceramics as scaffold materials is limited because of their inherent brittleness and difficult processability. The aim of this study was to create robust ceramic scaffolds, which have a desired architecture. Such scaffolds were successfully fabricated by projection‐based microstereolithography, and dilatometric analysis was conducted to study the sintering behavior of the ceramic materials. The mechanical properties of the scaffolds were improved by infiltrating them with a polycaprolactone solution. The toughness and compressive strength of these ceramic/polymer scaffolds were about twice those of ceramic scaffolds. Furthermore, the osteogenic gene expression on ceramic/polymer scaffolds was better than that on ceramic scaffolds. Through this study, we overcame the limitations of previous research on fabricating ceramic scaffolds and these new robust ceramic scaffolds may provide a much improved 3D substrate for bone tissue regeneration. Biotechnol. Bioeng. 2013; 110: 1444–1455. © 2012 Wiley Periodicals, Inc.     

In Vitro and In Vivo Evaluations of Nano-Hydroxyapatite/Polyamide 66/Glass Fibre (n-HA/PA66/GF) as a Novel Bioactive Bone Screw

In this study, we prepared nano-hydroxyapatite/polyamide 66/glass fibre (n-HA/PA66/GF) bioactive bone screws. The microstructure, morphology and coating of the screws were characterised, and the adhesion, proliferation and viability of MC3T3-E1 cells on n-HA/PA66/GF scaffolds were determined using scanning electron microscope, CCK-8 assays and cellular immunofluorescence analysis. The results confirmed that n-HA/PA66/GF scaffolds were biocompatible and had no negative effect on MC3T3-E1 cells in vitro. To investigate the in vivo biocompatibility, internal fixation properties and osteogenesis of the bioactive screws, both n-HA/PA66/GF screws and metallic screws were used to repair intercondylar femur fractures in dogs. General photography, CT examination, micro-CT examination, histological staining and biomechanical assays were performed at 4, 8, 12 and 24 weeks after operation. The n-HA/PA66/GF screws exhibited good biocompatibility, high mechanical strength and extensive osteogenesis in the host bone. Moreover, 24 weeks after implantation, the maximum push-out load of the bioactive screws was greater than that of the metallic screws. As shown by their good cytocompatibility, excellent biomechanical strength and fast formation and ingrowth of new bone, n-HA/PA66/GF screws are thus suitable for orthopaedic clinical applications.     

The effects of gelatin,fibrin-platelet glue and their combination on healing of the experimental critical bone defect in a rat model: radiological,histological, scanning ultrastructural and biomechanical evaluation

Fibrin-platelet glue (FPG) is a blood derivative, in which platelets and fibrinogen are concentrated in a small plasma volume, by differential centrifugation and precipitation. It can form a three-dimensional and biocompatible fibrin scaffold with a myriad of growth factors and proteins that are released progressively to the local environment and contribute to the accelerated postoperative bone healing. Gelatin (Gel) is a derivative of collagen and can promote cell adhesion and proliferation due to its unique sequence of amino acids, so it is suitable for bone tissue applications. This study examined the effects of Gel, FPG and their combinations as bone scaffold on the healing of surgically created critical-size defects in rat radius. Fifty critical size defects of 5 mm long were bilaterally created in the radial diaphysis of 25 rats. The animals were randomly divided into five equal groups as empty defect, autograft, Gel, FPG and Gel–FPG groups (n = 10 in each group). Radiographs of each forelimb were taken postoperatively on the 1st day and then at the 28th and 56th days post injury to evaluate bone formation, union and remodeling of the defect. After 56 days, the rats were euthanized and their harvested healing bone samples were evaluated by histopathology, scanning electron microscopy (SEM) and biomechanical testing. The results of present study showed that the Gel alone did not significantly affect bone healing and regeneration; however, the Gel treated defects promoted healing more than those that were left untreated (negative control). Furthermore, the FPG-enhanced grafts provided a good scaffold containing numerous growth factors for proliferation of osteoinduction and was effective in improving the structural and functional properties of the newly formed bone more than that of the untreated and also the Gel treated groups. Incorporation of Gel into the FPG scaffold improved healing potential of the FPG scaffold; however, it was still inferior to the autograft (positive control). Although the Gel–FPG scaffolds had best effectiveness during bone regeneration, it still needs to be further enhanced by incorporation of the ceramic and osteoinductive biomaterials.     

Biological properties of solid free form designed ceramic scaffolds with BMP-2: in vitro and in vivo evaluation

Porous ceramic scaffolds are widely studied in the tissue engineering field due to their potential in medical applications as bone substitutes or as bone-filling materials. Solid free form (SFF) fabrication methods allow fabrication of ceramic scaffolds with fully controlled pore architecture, which opens new perspectives in bone tissue regeneration materials. However, little experimentation has been performed about real biological properties and possible applications of SFF designed 3D ceramic scaffolds. Thus, here the biological properties of a specific SFF scaffold are evaluated first, both in vitro and in vivo, and later scaffolds are also implanted in pig maxillary defect, which is a model for a possible application in maxillofacial surgery. In vitro results show good biocompatibility of the scaffolds, promoting cell ingrowth. In vivo results indicate that material on its own conducts surrounding tissue and allow cell ingrowth, thanks to the designed pore size. Additional osteoinductive properties were obtained with BMP-2, which was loaded on scaffolds, and optimal bone formation was observed in pig implantation model. Collectively, data show that SFF scaffolds have real application possibilities for bone tissue engineering purposes, with the main advantage of being fully customizable 3D structures.     

The effects of mechanical stretch on the biological characteristics of human adipose‐derived stem cells

Adipose‐derived stem cells (ADSCs) are a subset of mesenchymal stem cells (MSCs), which have promised a vast therapeutic potential in tissue regeneration. Recent studies have demonstrated that combining stem cells with mechanical stretch may strengthen the efficacy of regenerative therapies. However, the exact influences of mechanical stretch on MSCs still remain inconclusive. In this study, human ADSCs (hADSCs) were applied cyclic stretch stimulation under an in vitro stretching model for designated duration. We found that mechanical stretch significantly promoted the proliferation, adhesion and migration of hADSCs, suppressing cellular apoptosis and increasing the production of pro‐healing cytokines. For differentiation of hADSCs, mechanical stretch inhibited adipogenesis, but enhanced osteogenesis. Long‐term stretch could promote ageing of hADSCs, but did not alter the cell size and typical immunophenotypic characteristics. Furthermore, we revealed that PI3K/AKT and MAPK pathways might participate in the effects of mechanical stretch on the biological characteristics of hADSCs. Taken together, mechanical stretch is an effective strategy for enhancing stem cell behaviour and regulating stem cell fate. The synergy between hADSCs and mechanical stretch would most likely facilitate tissue regeneration and promote the development of stem cell therapy.